1. Field of the Invention
The present invention relates to signal sensing circuit, and more specifically to a high-side signal sensing circuit.
2. Description of the Related Art
FIG. 1 shows a high-side signal sensing circuit 100 in conventional arts. The high-side signal sensing circuit 100 basically comprises an operational amplifier 110, resistors 120-160, and a LOAD 170. The voltage VH supplies power to the node between the resistor 120 and the resistor 140 such that current I140 flows through the resistor 140. Since the resistor 140 couples to the LOAD 170 and the negative input of operational amplifier 110 via the resistor 150, the current I140 would be divided into two currents, current I150 flowed through the resistor 150 and current ILOAD flowed through the LOAD 170. That is, the current ILOAD would be varied with the resistance value of LOAD 170 and resistors 120-150.
However, if the LOAD 170 is LEDs, the amount of current transmitted to the LOAD 170 would affect the illumination of LEDs; this means that the resistance value of resistors 120-150 would affect the illumination of LEDs when the voltage value of VH was adjusted, that is, the drawback of traditional approach, having resistors used as voltage divider for high-side signal sensing, is poor accuracy because of the temperature and process variation such that it is hard to control the illumination of LEDs and sense the load current ILOAD when the voltage value of VH was adjusted.
Therefore, how to control and sense the load current ILOAD has become an imminent task for the industries.